Signaling



Jan. 18, 1944. M. G. CROSBY 2,339,620

SIGNALING Original Filed June 20, 1932 2 She ets -Sheet 1 Fi Fly. 2.

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lNVE NTOR MURRAY 6- mass) BY F9? ATTORNEY Patente d'J an. 18, 1944 UNITED STATE SIGNALING Murray'G. Crosby, Riverhead, N. Y., a S S or to Radio Corporation of America, a corporation of Delaware Original application June 20, 1932, Serial No. 618,154. Divided andthis application October 23, 1940, Serial No. 362,331

12 Claims.

. In the drawings Figs. 1 and 2 are curves explanatoryof my present invention; and

Figs. 3, 4, 5, s and 7 illustratefilter circuits which may be included in the frequency modulated signal receivers of the prior figures to adapt themto efficient reception of phase modulated signals.

As explained in my copending application referred to above, frequency modulation wave directors may, in accordance with the present invention, be used for the reception of phase modulation waves. This is accomplished by adjusting the circuits for frequency modulation, as described in my parent application, and using a correcting filter r circuit at the receiver which has its output voltages inversely proportional to its input frequency so that its characteristic is .as shown in Fig. 1, wherein audio frequency impressed on the input terminals of thecorrection .circuit is plotted against Voltage output.

When phase modulated signals are received on a frequency modulation receiver, the signal output'of the frequency modulated receiver 'varies in. amplitude directly with the frequency of the signal at the input of thefrequency modulated signal receiver. Consequently, the audio fre-' quency output of this receiver would be distorted and would be lacking in low frequencies. The output of the receiver instead of being the same for all audio frequencies, as shown by the dotted line of Fig. 2', would be directly proportional to the frequency of the signals'impressed on the input of the receiver, as shownby the full line of Fig. 2. p

In order to compensate for this distortion of the signal frequency when phase modulatedsignals are received on a frequency modulated signal receiver,a filter circuit or correction circuit, a the amplitude of the signal frequency in the output of which is inversely proportional to the frequency ofthe signals impressed on the input of the-circuit, as indicated in Fig. 1 of the drawceiver for reception of phase modulated signals. The combination of the effect of a filter circuit or correction circuit having characteristics 'as illustrated by Fig. 1, with the effect of the inherent characteristics of a frequency modulated receiver on phase modulated signals, gives an over-all characteristic such as the dotted line of Fig. 2, which is a true reproduction of the signal wave applied as phase modulationto the carrier at the transmitter.

This correction filter or circuit CC.is used with the receiver and is connected after the detector as described in detail in my parent application. Various forms of filter or correction circuits, which will affect the signal frequencies passed therethrough in such a manner as to make the amplitude of the signals at the output thereof inversely proportional to the frequency of the signals applied to the input, may be'used. Seve eral preferred forms of correction circuits will now be described.

In Fig. 3 phase modulated 'waves picked up on the antenna are translated into signal waves by the frequency modulation receiver FMR such as described in my parent application. The correctingcircuit CC is added to reproduce an undistorted signal in jack J.' That is, in Fig. 3 the signal frequencies to be corrected are applied to the primary winding of a transformer 50 and are impressed from the secondary winding of said transformer on the input electrodes 52, 54

of a thermionic tube 5| to energize the same.,

The control electrode 52 of tube 5| is maintained at the desired operating potential by means of a biasing source 55. The anode electrode 56 of tube 5| is connected. through a parallel circiiit comprising a resistance 51 and capacity 58 to the cathode 54 by way of a high potential charging source 59.

ings, is utilized in accordance with the present invention to adapt a frequency modulatedrev The low frequencies of the signal potentials are emphasized by means of the capacity '58 connected across the resistor 51. The impedance of this resistance 51 andcapacity 58 in parallel is high at the lower signal frequencies and low at the higher signal frequencies. The amplification factor. of the tube 5|, which depends upon the external impedance of its anode cathode circuit, will be high at the lower signal frequencies and low at the higher signal frequencies. The signal frequency oscillations appearing on the anode of tube 5| are impressed therefrom by way of a coupling condenser Ell to the control g'rid 6| of -a thermionic amplifier 62. corrected signal frequency potentials are amplifled in'62 and appear in the primary winding 63 These distorted or of the transformer winding 64. Th corrected signal frequencies may be utilized from the secondary winding 55 of the transformer 63.

In order to operate 62 at the desired point on .its characteristic curve, biasing potential is supplied from the source 66 by way of resistance 61 to the control electrode 8| of tube 62.

If the single distortion or correction tube does not effect suflicient distortion or correction of the signal frequencies passed thereth'rough, a second-tube, connected in circuit and operated similar to tiibe 5|, may be connected in cascade with Si to apply more distortion or corrective eifect to the signal. This arrangement is shown in Fig. 4.

In Fig. 5 the signals to be corrected are impressed on the input winding of a transformer 50 and utilized from the secondary winding 65 of transformer 63 in the same manner as in the arrangement of Fig. 3. In Fig. 5, however, no

amplifier is shown connected with the correction.

tube 5!, although it is understood that the corrected signals can be further amplified, if necessary, by connecting the output of tube 5| with the input of a thermionic amplifier. The secondary winding of the transformer 50 is connected in where between full correction of the signal and parallel with the potentiometer resistance Ill in a order that the desired signal amplitude may be impressed on the input electrode 52 by way of the tap I I.

In this arrangement the resistance R: is of such a high impedance to the signal current as compared to the impedance of the capacity C2 to the signal current that the current passed through the circuits R2, C2 is governed mainly by the resistance of R2. This makes the current through the circuit elements C2, R2 constant with frequency so that the voltage across C: will be inversely proportional to the frequency of the applied signal, due to the fact that the'impedance of the condenser C2 varies inversely as the frequency of the signals applied across the terminals thereof vary. The potentials appearing at the terminals of C2 are impressed on the input.

electrodes 52, 54 of correction tube 5|.

In the arrangement shown in Fig. 6 correction is applied to the signal in the same manner in which correction is applied thereto by the arrangement shown in Fig. 5. However, in Fig. 6 a second-tube 5| is added for the purpose of varying the amount of distortion or corrective effect applied to the signal waves relayed therethrough. When tube 5| is switched oflz full correction will be obtained by means of the tube 5| in the same manner in whichcorrection is obtained in the arrangement of Fig. 5. with the tube 5! turned on, signal potentials the amphtude of which may be determined by the tap I l will be applied from the parallel resistance to the terminals of the resistance R4 by way of resistance R3. The resistances R2, R4 will affect all of the frequencies of the signal impressed thereon in like manner so that no corrective effect will be, applied to the signal appearing on the input electrodes 52' of the tube 5|. Consequently, the oscillations at signal .frequency, appearing on the anode 56 of tube 5| and applied therefrom to the transformer 64, will be the same for all frequencies and will represent in a normal manner the signal potentials applied at the input of the correction circuit. V

By moving the taps H and' 'II' along the resistances 10 and I0, the amount of corrected signal and-uncorrected'signal reaching the outputcircuit 63 can be adjusted to give the desired no correction.

This type of correction circuit is useful where it is desired that the transmitter radiate a combined frequency and phase modulated signal or a crossbetween frequency and phase modulated signal. Furthermore, such an arrangement is especially desirable where a correction circuit of this type is used in the signal amplifier circuits of the transmitter and a second correction circuit of this type is used subsequent to the detector in the receiver receiving signals from said transmitter.

In the correcting circuit shown in Fig. 7, as in the prior arrangements, the signals to be corrected are impressed on the transformer 5| and the corrected signals are utilized from the transformer 64. In this arrangement, however, a difierent means is provided for emphasizing the lower frequencies of the signal. The value of the inductance XL in series with the controlelectrode is so chosen that its impedance to the S nal frequency is high as compared to the impedance of the resistance R5 to the signal frequencies. The inductance XL then is-the governing factor of the circuit and-determines the intensity of the current passed through the circuits I, R5. Since the inductance XL offers a higher: impedance to the higher frequencies than to the lower frequencies, the current passing through the inductance XL will be inversely proportional to the frequency of the impressed signals. Consequently, the voltages at signal frequency, appearing across the resistance Rs, which are fed to the control electrode 52 of tube 5|, will be inversely proportional to the frequency of the impressed signals.

Having thus described my invention what I claim is:

1. The methodwhich includes these steps, amplifying each of the components of a band of frequencies an amount inversely proportional to its frequency, amplifying each of the components of said band of frequencies an amount which is constant with frequency, and combining the amplified wave portions.

- 2. The method which includes these steps, amplifying the components of a complex signali wave an amount such that theamplified wave varies inversely withfrequency, amplifying the components of said complex signaling wave an amount such that the amplified wave is constant with frequency, combining the amplified waves and modulating the instantaneous frequency of a high frequency carrier wave in accordance with the combined waves.

3. The method of signaling with a high frequency carrier .wave and signaling waves which includes the steps of amplifying said signaling wave in a way such that the amplified wave varies between a characteristic which 'is flat' or constant with frequency and a characteristic which is inversely proportional to frequency and modulating the highfrequency carrier wave in accordance with the amplified wave.

4. In an amplifying system for wave energy covering a given band of frequencies, a pair of amplifying stages each having input circuits and output circuits, connections for supplying said wave energy covering said band of frequencies,

- to the input circuits of said amplifiers and means signaling wave wave which includes these steps, ponents of an entire band of wave energy char! acteristic of said of said stages has a characteristic such that its output varies inversely with input frequency and the other of said stages has a characteristic such that its-output is constant with respect to input frequency.

5. An amplifier comprising a pair 'ofdischarge tube systems each having an anode, a cathode and -a control electrode, anodes effectively in parallel, an input circuit connected between the control grid and cathode of one of said tube systems having av characteristic' such that its output is inversely proportional to frequency, nected between the control grid and the cathode of the other tube system having a characteristic means connecting the 3 another input circuit con-- an amount which such that its output is constant with frequency,

a source of wave energy'to be amplified, said wave energy covering a predetermined band of frequencies and means for feeding wave energy covering said predetermined band of frequencies from said source through each of said input circuits to each of said tube systems.

6. Apparatus as claimed in the preceding claim characterized by the fact that awave amplitude attenuator is provided in at least one of said input circuits to relatively variably control the amount of the wave energy fed to the input circuits of said tube systems.

'7. The method of signaling which includes these steps, amplifying components of an entire band of wave energy characteristic of a complex an amount which is substantially inversely related to the frequency --of the various components, substantially uniformly amplifying components of-said e tire band of wave energy characteristic of saidcomplex signaling wave,

and combining the amplified waves.

8. The method of signaling by means of a high frequency carrier wave and a complex signaling amplifying comcomplex signaling wavean amount which'is substantially inversely related to the frequency of the various components, subs't'antially uniformly amplifying of said entire band of wave energy characteristic the components of said complex signaling wave, combining the amplified wave and modulating the instantaneous frequency of said high frequency carrier in accordance with the combined amplified waves.

9. The methodof operating with modulating potentials covering a band of frequencies which includes these steps, amplifying the potentials of said band of frequencies an amount substantially inversely proportional to their frequencies, amplifying the potentials of said band of frequencies is substantially uniform over the band, and combining the amplified potentials to derive modified modulating potentials.

' 10. The method of operating with modulatingpotentials covering a band of frequencies which includes these steps, amplifying the potentials of said band of frequencies an amount substantially inversely proportional to their frequencies, amplifying the potentials of said band of frequencies an amount which .is substantially uniform over the band, combining the amplified potentials, and relatively adjusting. the amount of amplification accomplished in said two amplifying steps to obtain modified modulating potentials.

, 11. The method of operating with wave energy of carrier wave frequency and modulating poteninversely proportional to ulating the instantaneous this covering a band of frequencies wh ich includes these steps, amplifying the potentials of said band of frequencies an amount substantially their frequencies, amplifying the potentials of said band of frequencies an amount which is substantially uniform over the band, combining the amplified potentials to derive modified modulating potentials and modfrequency of the wave energy of carrier wave frequency in accordance with the derived modulating potentials.

12. The method of operating with wave energy of carrier wave frequency and modulating?- tentials covering a band of frequencies which includes these steps, amplifying the potentials of said band of frequencies an amount substantially inversely proportional to their frequencies, am-

plifying the potentials of said band of frequencies an amount which is substantially uniform over the band, combining the amplified potentials, rel

atively adjusting the amount of amplification accomplished in said two amplifying steps to derive modified modulating potentials and modulating the instantaneous frequency of said wave-energy of carrier wave frequency in accordance with the derived modulating potential. 1

MURRAY G. CROSBY. 

